Every country is careful with rules like that. The main difference is the US has been the #1 destination for almost everyone in the world to work/live for decades, so it's a major supply/demand issue that border guards have to deal with. People often compare it to European countries. Random countries that are people's 15th choice to immigrate, where they don't need to try as hard with enforcement. Or at least didn't until recently, since Europe also began experiencing American-southern border style immigration issues.