R Shiny error: object input not found

I've solved this issue with "<<-". I don't know for sure, but it is related to global environment:

output$SpendChart <- renderPlot({

choice <<- input$split

    Country <- spend$Principal.Place.of.Performance.Country.Name
    ggplot(spend, aes(x = Country, y = choice)) + geom_bar(stat = "identity")

})

The problem is with ggplot evaluating the variable in the context of the data frame provided, spend in your case. What you want is:

ggplot(spend, aes_string(x = "Country", y = input$split))

So your working server.R code is:

library(shiny)
library(ggplot2)

shinyServer(function(input, output) {

spend <- data.frame(Country = c("Turk", "Turk", "Saudi", "Saudi", "Ger", "Ger"),
                    Action.Obligation = c(120,-345,565,-454, 343,-565),
                    Action_Absolute_Value = c(120,345,565,454,343,565))

    output$SpendChart <- renderPlot({


        ggplot(spend, aes_string(x = "Country", y = input$split)) +
            geom_bar(stat = "identity")

    })

})

Obviously, you can replace the spend df with your CSV import.