James P Hogan - Voyage From Yesteryear - There was a wave of colonization, and Earth more or less lost contact. Earth is in rough political shape, yet they send out 3 ships to re-establish contact. Trip took ~20 years outbound. Not sure how close to light speed they actually got.
There were 3 ships going out to re-establish contact-- "USA" "Chinese" "European" USA was first, the others followed with a year or 2 between.
There were interesting events on arrival at the colony planet-- they hadn't formed a government like Earth's; they did it their way. People on the USA ship who wanted to re-establish Earth-like government tried to do it by force and were eliminated. The USA ship and people were assimilated into the existing way of doing things. The 2nd and 3rd ships were greeted and assimilated in turn.
In the meantime, radio from Earth told the tale of cold wars becoming hot, with eventual story of the planet in turmoil, and contact from Earth lost. The colony planet updates the ship that brought the USA group to the colony, and were about to make a trip to Earth to see if anyone was still alive. The return trip would take "less than 1/3 the time the outbound trip had taken."
