Power Query - compare last two records.

Anonymous , Split column one create country and date column

Then you can have measures like

Current =

var _max = maxx(allselected(Table), Table[Country] = max(Table[Country]) ), Table[Date]) 

return

calculate(sum(Table[Value]), filter(Table, Table[Date] =_max) )

Previous =

var _max1 = maxx(allselected(Table), Table[Country] = max(Table[Country]) ), Table[Date]) 

var _max = maxx(allselected(Table), Table[Country] = max(Table[Country])  && Table[Date] <_max1 ), Table[Date]) 

return

calculate(sum(Table[Value]), filter(Table, Table[Date] =_max) )

We can also explore index function

with partition by country order by date desc

current=

 calculate(sum(Table[Value]), index(1, allselected(Table[Country], Table[Date]), orderBy(Table[Date], desc) ,partitionBy(Table[Country])))

prior=
calculate(sum(Table[Value]), index(2, allselected(Table[Country], Table[Date]), orderBy(Table[Date], desc) ,partitionBy(Table[Country])))