[rcxdude]

It is not legal in the US. If you're being paid to show or use something and there's no reasonable expectation that you would be, it must be disclosed. The FTC has guidelines on this and has gotten involved in the larger cases of this happening (such as the CS:Go skin gambling scandal where big streamers were being paid to stream gambling on the site, often a fake version with no actual risk and/or distorted rewards). You'll find most larger 'influencers' are aware of this and take steps to mention when something is sponsored, but there's a huge number of smaller ones where there's little enforcement.