Good catch. Try this instead
In[108]:=
fulltweets =
Lookup[Lookup[#, "retweeted_status", #] & /@
ImportString[response[[2]], "RawJSON"]["statuses"], "full_text"];
In[109]:= StringLength /@ fulltweets
Out[109]= {45, 19, 206, 223, 172, 263, 240, 131, 126, 60}