CHICAGO (AFP) - A Texas man offered a quite literal welcome sign for people of all backgrounds and political beliefs, amid increasingly caustic political discourse in the United States.

A billboard went up over the weekend in the city of Amarillo in the northern Texas plains with the message: "Texas is for everyone - not for bigotry. Welcome, y'all," using the popular Southern contraction for "you all." Amarillo is prime territory for a roadside message.

The small Texas city in the northern reaches of the strongly conservative state is bisected by a major interstate highway that takes drivers west to the battleground state of New Mexico and east to Republican-majority Oklahoma.

The billboard was the brainchild of resident Roman Leal, who was motivated by another sign posted just a week ago on the same interstate highway that said: "Liberals please continue on I-40 until you have left our great state of Texas." Leal started an online fundraiser to pay for his more inclusive billboard message. He raised more than US$3,800, easily surpassing his US$1,800 goal.

"We need a sign that represents the true, hospitable spirit of the great state of Texas," Leal said on his GoFundMe campaign website.

"It will be visible to travellers and commuters driving along the interstate in Amarillo, giving us a chance to put our best boot forward." Heightened political divisions have spilled over into the private sphere, as several officials from President Donald Trump's administration have been heckled or kicked out of restaurants over revulsion to the administration's now-reversed migrant family separation policy.

An immigration crisis on the border with Mexico - with Texas playing host to many immigrant detention centres - has heightened the tensions.

The Red Hen restaurant in Virginia became the target of a conservative boycott after it asked White House spokeswoman Sarah Huckabee Sanders to leave during a meal last week.

"Kind of amazed and appalled by the number of folks on Left who applauded the expulsion of @PressSec and her family from a restaurant," said David Axelrod, a former top aide to Trump's predecessor Barack Obama.

"This, in the end, is a triumph for @realDonaldTrump vision of America: Now we're divided by red plates & blue plates! #sad."