It has definitely been adjusted for the US. We’re obviously still reluctant to switch to metric units so our METARs are a metric-english hybrid. Compare EGKK in London and BOS in Boston, MA…
METAR EGKK 171150Z 02005KT 290V140 9999 SCT048 BKN070 10/M01 Q1020
METAR KBOS 171154Z 29005KT 8SM BKN070 12/08 A3008 RMK AO2 SLP186 T01170078 10122 20100 51016
Both wind speeds are in knots, but the US METARs report visibility in statute miles…I believe others around the world are km. We report altimeter with an “A” and in inches of mercury while others are with a “Q” and in mb/hpa. We do have sea level pressure reported in mb/hpa in the RMK (remark) section and is reported in tenths. SLP186 in this case is 1018.6mb. The 12/08 in the body of the report is temp/dew in