From the Kingdom Ministry's, generally July/August issues, I got the following figures for the number of memorial partakers in the USA. It is usually in the Service Report but a few were in the Branch Letter.
Note the July '78 Branch letter gives a figure for ''The incomplete attendance figures for the continental United States indicate that 1,258,837 were assembled, with 4,293 partaking''.
As you can see I couldn't find anything for 71, 89, 90 or 91.
The percentage of American anointed is around 44%, dwindling to about 41% as we get further down. I assume it is an even smaller percentage of the latest 11,202 partakers.
Nevertheless, Jehovah does seem a little partial towards those dwelling in the USA. You truly are blessed.
Year ...........Worldwide........ USA as per KM
1970............ 10500.......... 4609
1971............ 10384..........
1972............ 10350 ..........4559
1973............ 10523 ..........4720
1974............ 10723 ..........4707
1975............ 10550.......... 4610
1976............ 10187.......... 4388
1977............ 10080.......... 4363
1978............. 9762........... 4308*
1979 .............9727........... 4246
1980..............9564........... 4237
1981..............9601........... 4204
1982 .............9529........... 4206
1983 .............9292........... 4058
1984............. 9081........... 3953
1985............. 9051........... 3899
1986..............8927........... 3801
1987..............8808 ...........3733
1988 .............8685........... 3684
1989............. 8734
1990............. 8869
1991............. 8850
1992............. 8683........... 3602
1993............. 8693........... 3602
1994............. 8617........... 3535
* 1978 Continental USA = 4293