How to interpret fixed effects?
Fixed effects model is estimated as:
$$   y_{i t} − \bar{y_i} = ( X_{i t} − \bar{X_i} ) \beta + ( \alpha_i − \bar{\alpha_i} ) + ( u_{it} − \bar{u_i} )$$
So the country fixed effect is always relative to the average fixed effect.
If a country has negative fixed effect that means it is less productive than average country in your sample. If you choose different sample results might change.