Even if it was banned from every single exchange on the planet it is impossible to stop people from buying it.
Every crypto is one simple swap away from Monero (e.g. Litecoin, Bitcoin, Ethereum)
You can also still buy it directly with fiat using DEXs like Bisq or Haveno
In the US you can still buy Monero using traditional exchanges like Kraken or KuCoin for now if you don't care about KYC
https://paste.sethforprivacy.com/?e839f39d0171a97b#Cx6NMmUdH25dmkq2ux54gu6h4vEND28hkPohQY9aEEej