I know it was a common thing in WW1 to have people from the same town serve together. I would imagine, and correct me if I'm wrong please, but wouldn't towns lose many people all at once like that? Would that not cause a kind of loss of popularity with the war and support of it? If it did, did they change it during ww2 so towns wouldn't be as devastated by one battle?
For the U.S. Army, the majority of units did not have a regional or local character. The Selective Service system and the rest of the government manpower bureaucracy generally did not make any effort to group men together by place of origin. This wasn't done for political reasons, but to efficiently allocate manpower amongst industry, army aviation units,army service units and the Navy and Marine Corps.
There is however, an important exception to this general trend, which was the 18 National Guard divisions organized before the US entered the war. Since the US Army formed 89 divisions overall, the National Guard divisions were a significant fraction of the total Army mobilization. These divisions were formed from a specific regional area, for example the 29th Infantry Division was from Maryland, Virginia and Pennsylvania, with component units from even smaller localities. However, the mobilization process tended to reduce the local character of these units as the war dragged on. Several rounds of Cadres were extracted from National Guard divisions and assigned as the nucleus of other divisions to be created later in the mobilization plans, these men were replaced with recruits from the national manpower pool. The 30th Infantry division, ostensibly from Tennessee, Georgia and the Carolinas had about 50% of it's manpower from outside the south when it entered combat in June 1944, 4-5 years after it had entered federal service. After entering combat, the replacements it obtained were from anywhere in the US, further eroding the regional character of the division.
There are other exceptions like the 442nd Regimental Combat Team from Hawaii and California which had a regional character due to racial segregation of Japanese Americans. Perhaps other special units had similar local character, for idiosyncratic reasons.
Source: Mansoor, Peter R. "The GI Offensive in Europe: The Triumph of American Infantry Divisions 1941-1945" (despite the jingoistic title, this volume has a lot of good info about the training and organization of the US Army units and how that affected their combat performance, positively or negatively.)