If I may ...
Well, it seems that lawful permanent resident, does qualify, but still has to make $1,320 earn for 1 credit, for a maximum of 4 credits a year, and earn a total 40 credits in which to qualify, which is usually 10 years of full time working. However, classified, as a “qualified alien”, non-resident aliens, lawful permanent residents, will have money withheld from their benefit checks by the Social Security Administration as part of a broader set of rules governing payments to non-resident aliens. The SSA is required to withhold up to 30% of the maximum amount of the non-resident alien’s Social Security benefit that would be taxable under the rules, currently 85% of their benefit. This equates to non-resident aliens, ie non-US citizens, seeing 25.5% of their benefit being withheld. So I guess they aren't treated as full US citizens in that way.
Also, non-U.S. citizens, regardless of status, cannot vote in U.S. federal and local elections, cannot hold certain government jobs, and cannot serve on juries. Many federal and state government grants, scholarships, and other benefits are available only to U.S. citizens.