I should look more into cost of living in Portugal, maybe, but one of the other commenters mentioned housing prices being… high. In US, making ~$20,000 you’d be considered poor (maybe not “officially”) and probably pay zero federal tax and receive quite a bit of assistance.
$20k is technically above the US federal poverty line for a single person. I live in a state where anyone under $30k is considered low-income and qualifies for full benefits.