The language of a recent Supreme Court decision provides a useful reminder of how America has changed over the past 250 years and what has been the driving force behind those changes. 

It is something to think about as we celebrate another Fourth of July holiday to mark the founding of our nation.

The Supreme Court justices were considering a challenge by the Obama administration to the law Arizona enacted that would have enabled the state to detain and expel immigrants who crossed the border without legal documentation. 

That Arizona law was the inspiration for similar laws passed in Georgia and Alabama, reflecting the belief of some citizens that the federal government isn’t doing enough to stop the influx of immigrants who come here illegally.

The Supreme Court majority overturned most of the provisions of that Arizona law, ruling that immigration control is a function that has always been the responsibility of the federal government.

Justice Anthony Kennedy, a conservative appointee to the court, made an interesting observation in the majority opinion he drafted.

"The history of the United States is in part made of the stories, talents and lasting contributions of those who crossed oceans and deserts to come here," Kennedy wrote.

"The National Government has significant power to regulate immigration," he added. "With power comes responsibility, and the sound exercise of national power over immigration depends on the Nation’s meeting its responsibility to base its laws on a political will informed by searching, thoughtful, rational civic discourse."

Kennedy was noting the fact that our American society has been shaped and refined by the successive waves of immigrants who have come here from widely-differing cultures.

The court’s decision also confirms the reality of what the demographic numbers tell us.

There are probably more than 12 million immigrants residing illegally in the United States.  No matter what states like Arizona or Georgia may try to do, there is no plausible way to detain all of these people and suddenly deport them back to their country of origin. 

State Rep. Edward Lindsey (R-Atlanta), one of the GOP leaders of Georgia’s General Assembly, conceded as much in an email to his constituents.

"It is not practical to expect 12 million-plus illegal aliens to be rounded up and sent home — especially children who crossed the border with their parents and know no other country or culture but ours," Lindsey said.

Immigrants have always come to America, and their movement here in recent years has contributed to a trend in which a majority-white population has become more and more diverse.

Census officials report that during the past year this country reached a tipping point. Racial and ethnic minorities for the first time accounted for more than half of the children born in the United States.

According to the 2011 census estimates, 50.4 percent of children below the age of 1 year were Hispanic, black, Asian or a member of some other minority group.

Demographers project that the non-white percentage of the population will continue to grow for this reason: whites, who have a median age of 42, are older than ethnic groups like Hispanics, who have a median age of 27.6 and thus have a higher percentage of women who are of child-bearing age.

We see this growing diversity in Georgia. It is estimated that people from minority ethnic groups now make up 53 percent of the state’s population that is under the age of 18. Georgia’s minority youth population grew by more than 14 percent over the last 10 years.

There are political implications as well. In 2002, whites comprised 71 percent of the state’s registered voters. The number of registered voters who were self-identified as Hispanic was just 12,461.

Ten years later, the percentage of white voters has dropped to 60 percent. The number of Hispanic voters is 98,538, according to the most recent data from the secretary of state’s office.

That is the American story for this Fourth of July. We are a more diverse society than we have ever been before. We will become more diverse as time goes by. 

My hope is that all of us can have a "searching, thoughtful, rational civic discourse" about where we go as a nation, as Justice Anthony Kennedy implored.

(Tom Crawford is editor of The Georgia Report, an internet news service at gareport.com that reports on government and politics in Georgia. He can be reached at tcrawford@gareport.com.)